And do they actually say that? If so, in what context?
Yes several times.
Dbro actually said (after the birth of his first) 'mum and dad must be so excited' I replied 'of course they are' he then said 'no I mean really excited, no day is more special than when your first born has their own child' - he is their first born (yes he did use the phrase 'first born')
He is obsessed with the fact that as the oldest and because he is a male, he is more important to mum and dad. You would think we were royals and he heir to the throne.
My son and their son have their birthdays 5 days apart. Sil organised an entire day out, 8-6, for her ds birthday on my sons birthday. Then demanded no one came to my sons birthday meal because her sons was more important.
The year later she tried it again. We booked ds' birthday party the weekend before his birthday. Sent the invites 2 months before. She claimed she had no clue we were having a party on that date. Even though she told me she had put it in the family diary.
She also told me that she 'hates' working mothers and thinks they should be banned from having kids.
There are many many times they have done things like this.